The butterfly check valves with counterweight and oil cylinder are very reliable as they can regulate the closing time of the valve. These valves are applied in pipelines as non-return device, with flow allowed in one direction only. The butterfly check valves with counterweight are double eccentric type with tilting disc, the counterweight lever will facilitate the anti-hammer device and the oil cylinder will slow down the closure movement, to reduce any slam with noise. From DN 900 and up, they come with two counterweight levers and two oil cylinders, one on each side of the valve. Epoxy coated inside and outside, the double flanged butterfly valves can be installed in drinking water plants. NBR gasket seals are on the disc and can be replaced without dismantling the valves from the pipeline.